Abstract

Directional mid-IR (3-20µm) light sources are required for remote sensing spectroscopic applications in various fields such as medicine, environment and defense & security. Mid-IR supercontinuum (SC) sources are one of the most promising solution since they offer both wide spectral coverage and high spectral power density along with a good beam quality. For practical purposes, fiber-based sources are highly attractive due to their ruggedness, compactness and reliability. Recently, Gauthier et al. reported a new cost-effective approach by generating a SC from 2.6 to 4.2 µm via the amplification of 400 ps pulses at 2.8 µm in an Er:ZrF₄ fiber amplifier [1]. In later experiments, the SC spectral coverage was extended up to 5.4 µm and 8 µm by respectively cascading InF₃ or As₂Se₃ step-index fibers at the end of the Er-doped amplifier [2,3]. In all these demonstrations, the long-wavelength edge of the SC was limited by propagation losses (material or mode confinement). In this study, we report an order of magnitude improvement vs [3] in term of average power for a SC extending up to 8.9 µm (at -30 dB level) by using a 2.5 m low-loss multimaterial (AsSe/AsS) chalcogenide glass (ChG) step-index fiber having a high numerical aperture.

© 2017 IEEE